AC180 Ground wire?

Manual says “This product must be grounded before operation”.
None of my other Bluetti models have this Caution.
Why does this model need a ground, how to go about doing that and does Bluetti supply a cable with this model, since it is apparently Mandatory.

Just talked with customer support and they said the ground is not needed - they will be updating the user manual for AC180

After confirming with the technician, AC180 can be used without grounding.
Grounding would be safer or some loads require grounding. Grounding is required by safety regulations.